Braking control system

ABSTRACT

A vehicle braking system is disclosed in which the brakes are hydraulically actuated by the conventional master cylinder and optionally may be mechanically actuated by the usual lever arrangement. A valve is disposed in the fluid conduit interconnecting the master cylinder and the brake and the master cylinder reservoir. The valve is responsive to actuation of the mechanical actuator to shift from a first position preventing communication to the reservoir to a second position preventing communication from the master cylinder into the valve and venting the brakes to the reservoir.

United States Patent 1 Chevreux 1 Apr. 3, 1973 [54] BRAKING CONTROLSYSTEM [75] Inventor: Gerard Chevreux, Bois-Colombes,

France [73] Assignee: Societe Anonyme D. B. A., Clichy,

France 221 Filed: July 24,1970

21 Appl.No.: 62,001

[30] Foreign Application Priority Data Aug. 1, 1969 France ..6926486[52] US. Cl. ..303/l3, 188/106 F, 303/9 [51] Int. Cl. ..B60t 15/16 [58]Field of Search....l88/l06 R, 106 P, 106 F, 170; 303/2, 7, 9,13, 89

3,485,537 12/1969 Schlor et al. ..188/106 FX 3,463,276 8/1969 Brooks,Jr. 3,488,096 1/1970 Hoopes ..303/9 Primary Examiner-Milton BuchlerAssistant Examiner-Stephen G. Kunin- Attorney-W. N. Antonis and Flame,Hartz,Smith and Thompson [57] ABSTRACT A vehicle braking system isdisclosed in which the brakes are hydraulically actuated by theconventional master cylinder and optionally may be mechanically actuatedby the usual lever arrangement. A valve is disposed in the fluid conduitinterconnecting the master cylinder and the brake and the mastercylinder reservoir. The valve is responsive to actuation of themechanical actuator to shift from a first position preventingcommunication to the reservoir to a second position preventingcommunication from the master cylinder into the valve and venting thebrakes to the reservoir.

4 Claims, 1 Drawing Figure BRAKING CONTROL SYSTEM This invention relatesto a braking control system for controlling actuation of at least onebrake mechanism provided with two separate brake actuating means.

In the prior brake mechanisms wherein the primary and the secondarybrake actuating means are controlled by a service and an emergencybraking control circuits respectively, it has been noted that the commonactuating of these two separate circuits generally results in anadditive effect of the respective braking forces generated by the twoindependent brake actuating means and thereby in an excessive resultanteffort on each of the braking elements of the brake mechanism. Theseefforts may cause a permanent deformation of any one of the brakingelements of this mechanism such as the drum of a drum brake or thestirrup of a disc brake mechanism since, in most cases, the emergencybraking control circuit is provided with locking means adapted tomaintain same in its brake applied position. In that latter case, itwill be also understood that all the braking efforts are substantiallyonly supported by the secondary braking actuating means and by theemergency braking control circuit controlling same after the servicebraking actuation has been released. Thus, theemergency or parkingcontrol circuit is maintained under excessive stresses that resulting inan abnormal wear and even in an eventual breaking of its various forcetransmitting elements such as cables, levers, gears, conduits, etc. Incertain cases, due to the above stresses and forces, it may be alsodifficult to actuate the above mentioned locking means or vthe emergencycontrol circuit to release the brake mechanism.

Furthermore, when using some particular braking mechanisms of the typewherein the secondary brake actuating means does not operate in parallelrelationship with the primary brake actuating means, it has been notedthat a normal control of these latter means generally prohibits a normalcontrol of the secondary actuating means by the emergency control,circuit at that time due to the substantial locked positions of thebrake friction elements actuated by said primary means. In other words,during a service application by the primary brake actuating means of thebrake mechanism, the various movable elements thereof are so positionedand subjected to such reaction forces that the secondary brake actuatingmeans cannot, at that time, normally actuate and/or position these brakeelements as they do in the absence of the primary braking controlactuation. In particular, in the event the emergency braking controlcircuit consists in a mechanical transmission controlled by a hand leverprovided with non-releasing locking means, it will be easily understoodthat the emergency circuit, if actuated during a service brakeapplication, is not capable of maintainemergency braking controlcircuit, respectively characterized in that a pressure relief valvecontrolled by said emergency braking control circuit is operativelyprovided in said service braking control ,circuit for terminating thenormal braking fluid ,pressure supply to said primary brake actuatingmeans and for connecting same to a relatively low fluid pressurereservoir upon actuation of said emergency braking control circuit.

Other features and advantages of the invention will appear from thefollowing description taken in connection with the accompanying drawingin which the single FIGURE is a diagrammatic view of a vehicle brakingcontrol system according to the invention.

I When considering the single FIGURE of the drawing, reference numeral 8designates a braking fluid pressure control source, such as aconventional master cylinder, adapted, when actuated by a brake pedal10, to control a variable fluid braking pressure to a service or primarybraking control circuit 12 including two sets of brake mechanisms 18 and20 relating for instance to the front and rear axle wheels of thevehicle, respecing the vehicle brake mechanism in its applied braketively.

In the shown embodiment, the brake mechanisms 18 and 20 are of thepivoting shoe drum brake type, the respective wheel cylinders 14 and 16of which are connected to the master cylinder 8 by fluid conduits 22 and24 respectively. At least one of the brake mechanisms 20 is alsoprovided with a second brake actuator device 26 operatively connected toan emergency or secondary braking control circuit 28 including apivoting hand lever 30 and mechanical force transmitting means, such asa cable 32, adapted to move the input control lever member 34 ofactuator 26 upon control pivotal displacement of hand lever 30 about itspivot axis 36. In the shown embodiment, the second actuator 26 iscomprised of a cam 26 pivotally mounted on the backing plate of drumbrake 20 and operatively located between the free ends of the two brakeshoes 31, 33 of brake mechanism 20 to be capable of urging these endsapart from one another upon pivotal displacement of input lever 34operatively secured to cam 26.

With the above described braking system, it will'be easily understoodthat the actuation of the service braking circuit 12 by means of brakepedal 10 substantially prohibits a normal operation of the emergency orparking braking system 28 by means of hand lever 30. As a matter offact, as long as the service braking pressure is maintained in brakeactuators 14, 16 and thereby as long as the trailing shoe 3] of brakemechanism 20 is hardly urged in engagement with the brake actuating cam26, this latter cannot be actuated by lever 34 to the extent to maintainthe brake mechanism 20 in its fully or even partially applied positionwhenever the service braking control pressure in actuator 16 isreleased.

With a view to avoiding the above drawback, the invention provides abraking pressure relief valve, designated as at 38, located in the fluidconduit 24 and operative to connect the fluid brake actuators 16 to arelatively low fluid pressure reservoir 40 such as the hydraulicreservoir of master cylinder 8, upon actuation of the emergency brakingsystem 28. To this end, the valve housing 38 is provided with a tippingvalve 42 adapted to control the communication from an inlet chamber 44connected to master cylinder 8 to an outlet chamber 46 connected toactuators 16 as a function of the axial position of a flange 47 on amovable valve actuating plunger 48 slidably mounted in chamber 46 toprotrude externally to housing 38. Plunger 48 is operatively connectedat its free outer end to lever 30 by means of a tensible spring 49 andis provided at its opposite end with. a check valve 50 controllingcommunication from outlet chamber 46 to exhaust orifice 52 connected tolow pressure reservoir 40. A compression spring 54 is provided betweenhousing 38 and flange 47 to normally urge valve 50 toward its closedposition.

The operation of valve 38 is as follows: upon pivotal controldisplacement of hand lever 30, plunger 48 is urged toward the left, asseen in the drawing, that causing closing of valve 42 and simultaneousopening of valve 50 for thereby releasing the braking pressure if any,in the brake actuators 16, and permitting a normal actuation of thebrake actuation cam 26.

As easily understood, the spring 54, in the normal rest position, asshown, of plunger 48, will be advantageously provided with apredetermined load to prevent inopportune actuation of plunger 48 byspring 49 as long as the brake hand lever 30 remains near from its brakereleasing position.

I claim: 1. In a vehicle braking system: a brake having hydraulicallyactuated applying means and mechanically actuated applying means;

operatoboperated fluid pressure generating means for actuating saidhydraulically actuated applying means;

mechanically actuated control means for actuating said mechanicallyactuated applying means;

a fluid reservoir operably connected to said fluid pressure generatingmeans; and

valve means independent of said operator-operated fluidpressuregenerating means including a housing having an inlet port communicatedto said fluid pressure generating means, a first outlet portcommunicated to said hydraulically actuated applying means, a secondoutlet port communicated to said fluid reservoir, and valve structurewithin said housing operably connected to said mechanically actuatedcontrol means, said valve structure shifting from a first positioncommunicating said inlet port with said first outlet port and preventingcommunication through said second outlet port to a second positionventing said first outlet port to said second outlet port upon actuationof said mechanically actuated control means.

2. The invention of claim 1:

said valve structure preventing communication between said inlet portand said first outlet port when said valve members are shifted to saidsecond position.

3. The invention of claim 2; and

resilient means yieldably urging said valve structure to said firstposition.

4. The invention of claim 2:

said housing defining a chamber therewithin, said inlet and outlet portscommunicating with said chamber, said valve structure including a firstvalve member slidably mounted in said chamber, said resilient meansyieldably urging said first valve member toward a position preventingcommunication through said second outlet port, said valve

1. In a vehicle braking system: a brake having hydraulically actuatedapplying means and mechanically actuated applying means;operator-operated fluid pressure generating means for actuating saidhydraulically actuated applying means; mechanically actuated controlmeans for actuating said mechanically actuated applying means; a fluidreservoir operably connected to said fluid pressure generating means;and valve means independent of said operator-operated fluid pressuregenerating means including a housing having an inlet port communicatedto said fluid pressure generating means, a first outlet portcommunicated to said hydraulically actuated applying means, a secondoutlet port communicated to said fluid reservoir, and valve structurewithin said housing operably connected to said mechanically actuatedcontrol means, said valve structure shifting from a first positioncommunicating said inlet port with said first outlet port and preventingcommunication through said second outlet port to a second positionventing said first outlet port to said second outlet port upon actuationof said mechanically actuated control means.
 2. The invention of claim1: said valve structure preventing communication between said inlet portand said first outlet port when said valve members are shifted to saidsecond position.
 3. The invention of claim 2; and resilient meansyieldably urging said valve structure to said first position.
 4. Theinvention of claim 2: said housing defining a chamber therewithin, saidinlet and outlet ports communicating with said chamber, said valvestructure including a first valve member slidably mounted in saidchamber, said resilient means yieldably urging said first valve membertoward a position preventing communication through said second outletport, said valve structure further including a second valve membernormally permitting communication through said inlet port, but beingresponsive to movement of said first valve member to terminatecommunication through said inlet port.